SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c38ccc9bd2d0df1f04123149c33ac8bc2e978b076f4f887cf421d035b399c5d' 
  AND token = 'omzM8MqhTIiWKExk+bGUmKr1wEg6ZvsNSiYGtTDLI6A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}